Lubricating oil composition



United States 3,030,303 LUBRICATING OIL CGMPGSITION Julian G. Ryan, Wood River, Ill., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 9, 1957, Ser. No. 651,598

5 Claims. (Cl. 252-33.6)

This invention relates to lubricating oil compositions, and more particularly to highly detergent lubricating oil compositions which also possess good load carrying and high temperature stability properties.

Recently it has been discovered that whereas met-ab containing detergents such as metal organic carboxylates, naphthenates and/or sulfonates are effective as detergents for lubricating oils within a restrictive temperature range, certain non-ash forming oil-soluble polymeric detergents, namely oil-soluble nitrogen-containing polymers such as copolymers of higher alkyl acrylates e.g. lauryl methacrylate and polymerizable nitrogne-containing compounds such as vinyl pyridines, N-vinyl lactams, acrylamides and the like, impart excellent detergency to lubricating oils over a wider temperature range than do metal-containing detergents. However, these non-ash forming polymeric detergents lack load carrying properties as do the metal-containing detergents mentioned above and at extremely high temperatures become unstable causing ring sticking, sludging and increase in viscosity.

H Certain organic phosphates, thiophosphates, sulfurized fatty materials and chlorinated organic compounds which are effective load carrying agents and/or stabilizers in lubricating oil compositions containing metal-containing detergents such as metal organic sulfonates, are inefiective for this purpose in lubricating oil compositions condetergents.

It has now been discovered that load carrying and stabilizing properties are imparted to lubricating oil compositions containing non-ash forming nitrogen-containing polymeric detergents, by addition thereto of a small amount of an oil-soluble group II of the periodic table divalent metal aliphatic dithiocarbamate. The imparting of these properties to lubricants containing non-ash nitrogen-containing polymeric detergents which lack load carrying and high temperatures stability properties, by the above-class of aliphatic dithiocarbamates which, as is known in the art, normally function as anti-oxidants and corrosion inhibitors, is unusual. The manner or mechanism whereby this additive combination functions is not clearly understood, but the unusual manner in which these two additives act and the unexpected properties which they impart to lubricants are evidenced by the test results presented hereinbelow.

The oil-soluble nitrogen-containing polymeric detergents are characterized in that they are essentially straight chain aliphatic hydrocarbon polymers having attached indirectly, through an oxygen-containing polar group, to the main hydrocarbon chain, a plurality of the same or different oleophilic alkyl radicals having at least 8 carbon atoms, and attached to different carbons of the main hydrocarbon chain a plurality of radicals containing nitrogen, preferably such that the oleophilic alkyl radicals are predominant to the nitrogen-contaim'ng radicals. The polymerizable monomer reactants are used in the mol ratio of from 1:10 to 10:1 and preferably from 1:1 to 1:7 of the nitrogen-containing polymerizable compound to the polymerizable material containing an oleophilic radical, respectively. The polymeric detergents range in molecular weight from 50,000 to over 2 million as determined by the light scattering method.

'taining non-ash forming nitrogen-containing polymeric 3,030,303 Patented Apr. 17, 1962 The detergent polymers are derived from at least two different polymerizable compounds, one of which contains an oleophilic alkyl radical of from 8 to 22 carbon atoms which is not part of the main hydrocarbon chain, and at least one polymerizable ntirogen-containing compound. The polymers may be derived from different polymerizable compounds as above and optionally also from one or more additional polymerizable compounds which can be analogous of the above polymerizable compounds or be of entirely diflerent classes.

Polymerizable monomers containing oleophilic components containing an aliphatic hydrocarbon chain of at least 8 carbon atoms which is not part of the main hydrocarbon polymer chain include polymerizable esters, ethers, acids, and mixtures thereof. Suitable esters include acrylic acid (including esters of acrylic acid and of alphaalkyl-substituted acrylic acid, preferably of from 3 to 4 carbon atoms) and aliphatic alcohols of at least 8 carbon atoms and preferably of from 12 to 20 carbon atoms such as decyl acrylate, lauryl acrylate, stearyl acrylate, eicosanyl acrylate, docosanyl acrylate, decyl methacrylate, lauryl methacrylate, cetyl methacrylate, stearyl methacrylate, and the like and mixtures thereof.

Other esters include the vinl esters of long-chain carboxylic acids such as vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate and the like and mixtures thereof; long-chain esters of vinylene dicarboxylic acids such as methyl lauryl fumarate and the like.

These components can be employed alone or in various combinations and, in general, make up the majority of the polymeric additive in order to insure good oil solubility. The technical lauryl methacrylate obtained from the commercial mixture of long-chain alcohols in the C to C range derived from coconut oil is an especially useful oleophilic component of the copolymer but the group of acrylic and alkacrylic esters of aliphatic alcohols of at least eight carbons are, in general, well suited as the oleophilic component of the copolymer.

The nitrogen-containing component of the polymers, can be introduced through the use of appropriate copolymerizable monomers containing primary, secondary or tertiary amino. nitrogen or nitrogen-containing heterocycles which are attached ultimately to the chain of the polymer as part of the extra substituent group.

Particular examples of the nitrogen-containing monomers include the amino substituted olefins such as p-(bet-adiethylaminoethyl)styrene; basic nitrogen-containing heterocycles carrying a polymerizable ethylenically unsaturated substituent, e.g. the vinyl pridines and the vinl alkyl pyridines such as 2-vinyl-5-ethyl pyridine; 2-methyl-5- vinyl pyridine, 2-vinyl-pyridine, 3-vinylpyridine, 4-vinylpyridine, 3-rnethyl-5-vinylpyridine, 4-methyl-2-vinylpyridine, 4-ethyl-2-vinylpyridine and Z-butyl-S-vinylpyridine and the like.

N-vinyl lactams are also suitable, and particularly when they are N-vinyl pyrrolidones or N-vinyl piperidones. The vinyl radical preferably is unsubstituted (CH =CH-), but it may be mono-substituted with an aliphatic hydrocarbon group of 1 to 2 carbon atoms, such as methyl or ethyl.

The vinyl pyrrolidones are the preferred class of N -vinyl lactams and are exemplified by N-vinyl pyrrolidone, N-( l-methylvinyl) pyrrolidone, N-vinyl-S-methyl pyrrolidone, N-vinyl-3,3-dimethyl pyrrolidone, N-vinyl-S-ethyl pyrrolidone, N-vinyl-4-butyl pyrrolidone N-ethyl-3-vinyl pyrrolidone, N-butyl-S-vinyl pyrrolidone, 3-vinyl pyrrolias the alkyl and cycloalkyl substituted aminoalkyl and cycloalkyl substituted aminoalkyl and cycloalkyl esters of the acrylic and alkacrylic acids, e.g. beta-methylaminoethyl acrylate, 4-diethyl-aminocyclohexyl methacrylate, beta, beta-didodecylaminoethyl acrylate, and the like; unsaturated ethers of amino alcohols such as the vinyl ethers of such alcohols, 'e.g. beta-aminoethyl vinyl ether, beta-diethylaminoethyl vinyl ether, and the like; amides of unsaturated carboxylic acids wherein an amino substituent is carried on the amide nitrogen such as N(betadimethylaminoethyl) acrylamide; polymerizable unsaturated amines, e.g. diallylamine, and they like.

These detergent polymers may contain variable but substantial amount of from about 5 to 30% based on the final product of other polymerizable components such as vinyl and allyl formates, acetates, propionate's, butyrates, and the like; polymerizable unsaturated'short-chain hydrocarbons, e,g. the. monoolefins such. as ethylene, propylene, isobutylene, styrene, vinyltoluene, and the like and the short-chain'dienes such as. '1,3'-buta'diene, isoprene, and the like; unsaturated short-chain carboxylic acids and their derivatives such as the alpha-methylene-carboxylic acids and their derivatives, e.g. acrylic acid, methyl methacrylate, butyl methacrylate, acrylonitrile, methacrylamide, and the like; the short-chain unsaturated ethers, particularly the vinyl and allyl ethers, e.g. ethyl vinyl ether, butyl vinyl ether, and the like.

The polymers can be prepared by any suitable means such as described in US. patent application Serial No. 571,612, filed March 15, 1956, and U.S. Patent 2,737,452.

The following examplesillustrate polymer additives which are'useful in compositions of this invention.

EXAMPLE I of 750,000 and was soluble in hydrocarbon oils.

EXAMPLE II A mixture of 2.52 mol of stearyl methacrylate, 5.04 mol of lauryl methacrylate, 0.83 mol of methyl methacrylate and 1 mol of Z-methyl-S-Vinyl-pyridine and 0.2% wt. of alpha, alpl1a'-azodi-isobutyronitrile dissolved in a minor amount of acetone for solubility was placed in a reaction vessel and reacted for about 24-48 hours at 65 C. with stirring in a nitrogen atmosphere. The polymer was then dispersed in equal volumes of benzene and thereafter precipitated with 5-10 volumes of a mixture of acetone and methanol. This was repeated and a stearyl methacrylate/lauryl methacrylate/methyl methacrylate/Z-methyl-S-vinylpyridine polymer having a nitrogen content of 0.60% by Weight and a molecular weight in excess of 750,000 was recovered.

EXAMPLE III A mixture of about 6 moles of lauryl methacrylate, 1 mole of N-vinyl pyrrolidone and 0.5% by weight of benzoyl peroxide was reacted in a suitable reaction vessel for a period of about 10 hours at about 65 C. The polymer was then dispersed in benzene and thereafter precipitatedwith a mixture of acetone and methanol. This was repeated and a copolymer of lauryl methacrylate/N- vinyl pyrrolidone having a nitrogen content of 0.45% by weight and a molecular weight in excess of 250,000 was recovered. The polymer contained the monomer units in the ratio as provided in the mixture.

EXAMPLE IV- A mixture of i020 parts of technical lauryl methacry- VII late, parts of methacrylanilide, 60 parts of beta-diethylaminoethyl methacrylate, 300 parts of mineral oil and 3.6 parts of alpha, alpha'-azodiisobutyronitrile was agitated together at 60i2 C. under nitrogen. After two hours some thickening of the charge was observed and during the next 16 hours, 900 parts more of mineral oil was added gradually as the polymerization proceeded. There was thus obtained a barely stirrable oil solution of a copolymer of the three polymerizable components in essentially the mole proportions charged, i.e. 86.4/ 8.5/5.1.

The technical lauryl methacrylate used in the preparation above is the methacrylic acid ester of technical lauryl alcohol which is obtained by reduction of the fatty acids of coconutoil and is a mixture of saturated straight chain alcohols ranging from about 10 to 18 carbon atoms. A typical example will contain approximately 3%.C 61% C12, CH' C15 C18 alcohols.

Following essentially the procedure of the above examples other polymers were prepared from monomer mixtures in the molar group, proportions as shown in Table I.

Table I Example SMAI L via YMMA MVP NVP s.

.2 V 2.8 as '1 X- p 4. 1- 2 dine; NVP =N-vinyl pyrrolidone; S=styrene.

Theload carrying and stabilizing agents .areoil-soluble" group II of the periodic table divalent metal aliphatic (acrylic and alicyclic) dithiocarbamatesand preferably alkyl dithiocarbamates, thev cationic portion of the salt being the group II divalent metals having an atomic number of 20 through 56 and more preferred .the group II B metals having an atomic number 30 through 48' i.e. zinc and cadmium. Examples of such compounds include the. Ca, Ba, Zn or Cd dipropyl dithiocarbamate, dibutyl dithiocarbamate, diamyl dithiocarbamate, dihexyl dithioe carbamate, dioctyl dithiocarbamate, di-Z-ethylhexyl dithiocarbamate, di-isobutyldithiocarbamate, diisoamyldithiocarbamate, N-amyl-N'-methyl dithiocarbamate, N methyl-N-octyl dithiocarbamate, N-octyl-N'-butyl dithiocarbamate, N-n-amyl-N-2-methylbutyl dithiocarbamate, N-n-amyl-N'-3-methylbutyl dithiocarbamate, N-octyl-N- 2-ethylhexyl dithiocarbamate, N-ethyl-N-phenyl dithiocarbamate, dicyclohexyl-dithiocarbamate, diphenyl dithiocarbamate, and the like as well as mixtures of these salts. The preferred are the Zn and Cd diamyl. and di-Z-ethylhexyl dithiocarbamates.

The mineral lubricating oils used in compositions of this invention can be obtained from any parafiinic, naphthenic,.asphaltic or mixed base crude, and/or mixtures thereof. The viscosity of these oils may vary over a wide range, such as from 100 SUS at 100 F. to 100 SUS at 210 F.

Mineral lubricating oils which are particularly desirable for use in compositions of the invention can be obtained from West Texas Ellenburger crudes, East Texas crudes, Oklahoma crudes, California crudes. A useful solvent refined East Texas mineral lubricating oil had the following properties Pour point, F

Viscosity centistokes; at 100 Fa.. Viscosity index The additive combination is effective in lubricating oil compositions in amounts ranging from about 0.1% to about and preferably from about 0.5% to 6% by weight each, based on the final lubricating oil composition.

Preferred compositions of this invention are illustrated by the following:

COMPOSITION A Percent, wt. Copolymer of Example III 5.5 Zn diamyl dithiocarbamate 0.4 Mineral lubricating oil Balance COMPOSITION B Percent, wt.

Terpolymer of Example H 5.5 Zn diamyl dithiocarbamate 0.4 Mineral lubricating oil Balance COMPOSITION C Percent, wt. Copolymer of Example III 5.5 Cd diamyl dithiocarbamate 0.5 Mineral lubricating oil Balance COMPOSITION D Copolymer of Example III 5.5% wt. Zn diamyl dithiocarbamate 0.5% wt. Zn dimethylcyclohexyl thiophosphate 0.92% wt. Basic Ca petroleum sulfonate 1.0% SA. Bright stock 6.0%. Mineral lubricating oil Balance.

COMPOSITION E Terpolymer of Example VII 5.5% wt. Zn diamyl dithiocarbamatc 0.5% wt. Zn dimethylcyclohexyl thiophosphate 0.92% wt. Basic Ca petroleum sulfonate 1.0% SA. Mineral lubricating oil Balance.

COMPOSITION F Copolymer of Example I 5.5% wt. Zn diamyl dithiocarbamate 0.4% wt. Zn dimethylcyclohexyl thiophosphate 0.92% wt. Basic Ca petroleum sulfonatc 1.0% SA. Mineral lubricating oil Balance.

The outstanding properties of compositions of this invention are shown in Table II when they were tested in the Timken machine for load carrying properties and in the Cadillac engine under heavy duty highway-cycle test and in the COT engine 80-hour high-temperature test for cleanliness, corrosion and overall engine conditions.

The Timken Test is described in the SAE Journal 28,

B. COT ENGINE (CRC SINGLE CYLINDER ENGINE) R.p m 2800 Jacket temp F-.. 375' Oil temp F 275 Carburetor air temp F 110 Time hours 80 Table 11 Cadillac Test 1 COT Tim- Eng. Composition ken Intake Test Load, Sludge Overall Valve Bearlbs. Rating Rating Deposmg wt it loss Ratin D (present invention) 28 91 85 E (present invention) 28 95 90 80 Composition X 2 16 60 78 68 A (present invention) 30 267 Mineral lubricating oil 10 50 50 60 l, 157

1 =pcrfeet; 0=p0or. 1 Composition X is same as composition D except it contained no Zinc diamyl dithiocarbamate.

Compositions B, C, E and F when tested in the Timken machine and in the Cadillac engine gave results similar to composition D. Also compositions B, C, D, E and F when tested in the COT engine efiectively inhibited corrosion and the engine was clean and in good condition. On the other hand when the zinc dialkyldithiocarbamate was omitted from these compositions and tested as described above load carrying properties were poor (about same as for composition X) and the engines were in poor condition at the end of these tests.

The additive combination of this invention is useful for providing superior detergent and wear inhibiting properties to lubricating oils which contain small amounts (0.1% to 3%) of other agents such as metal dithiophosphates (Zn alkyl dithiophosphate) metal organic sulfonates, e.g. neutral or basic Ca, Ba or Zn petroleum sulfonate, amines such as phenyl-alpha-naphthylamine, octadecylamine, alkyl phenol, viscosity-index improvers and pour point depressants such as the Acryloids, and specifically, Acryloid, 150, 618, 710, and/or 768, made by Rohm and Haas and described in US. Patent 2,710,842; condensation products of chlorinated parafiin wax and naphthalene; extreme pressure agents such as amine salts of trichloromethane phosphinic acid, its ester, amides or amine salts; organic sulfides and mixtures thereof.

Compositions of this invention are used as engine oils, turbine oils, gear oils, and in various other fields of lubrication Where detergency and wear inhibiting properties are essential.

I claim:

1. A lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 0.1% to about 10% of an oil-soluble copolymer selected from the group consisting of (1) a copolymer of a C alkyl methacrylate and a vinylpyridine in the mol ratio of 1:1 to 7:1, respectively, and (2) a C1240 alkyl methacrylate and a vinylpyrrolidone in the mol ratio of 1:1 to 7:1, respectively, the copolymer having a molecular weight of from 50,000 to 2,000,000 and a minor but load carrying and stabilizing amount of an oilsoluble divalent metal salt of a dialkyl dithiocarbamic acid, the divalent metal being selected from the group consisting of Zinc and cadmium.

2. A lubricating oil composition consisting essentially of a major amount of a mineral lubricating oil and from about 0.5 to about 6% of an oil-soluble copolymer of a C1240 alkyl methacrylate and vinylpyrrolidone in the mol ratio of 1:1 to 7:1, respectively, and having amolecular weight of from 50,000 to 2,000,000 and a minor, but loadcarrying amount, of an oil-soluble zinc dialkyl dithiocarbamate.

3. A lubricating composition consisting essentially of a major amount of a mineral lubricating oil and from about 0.5 to about 6% of a copolymer of lauryl methacrylate/Z-methyl-S-Vinyl-pyridine in the mol ratio of 1:1 to 7 :1, respectively, and having a molecular weight of 7 from 50,000 to 2,000,000 ancl.-from about 0.5% to about 6% byweight of zinc diamyl dithiocarbamate.

4. A lubricating composition consisting essentially of a major amount of a mineral lubricating oil and from about 0.5 to about 6% of a copolymer of stearyl methacrylate/vinyl pyrrolidone in' the mol ratio of 1:1 to 7:1, respectively, and having a molecular weight of from 50,000 to 2,000,000 and from about 0.5 to about 6% by weight of zinc dlamyl dithiocar-bamate.

5. A lubricating composition consisting essentially of a major amount of a mineral lubricating oil and'from about 0.5% to about 6% of a. copolymer of lauryl methacrylate/vinyl pyrrolidone in the mol ratio of 1:1 to 7:1, respectively, and having'a molecular weight of from 50,000

8 to2,000,000 and from about 0.5 to about 6% by weight of zinctdiamyl dithiocarbamate,

ReferencesCited in the file of this patent;

UNITED STATES PATENTS 

1. A LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF MINERAL LUBRICATING OIL AND FROM ABOUT 0.1% TO ABOUT 10% OF AN OIL-SOLUBLE COPOLYMER SELECTED FROM THE GROUP CONSISTING OF (1) A COPOLYMER OF A C12-20 ALKYL METHACRYLATE AND A VINYLPYRIDINE IN THE MOL RATIO OF 1:1 TO 7:1, RESPECTIVELY, AND (2) A C12-20 ALKYL METHACRYLATE AND A VINYLPYRROLIDINE IN THE MOL RATIO OF 1:1 TO 7:1, RESPECTIVELY, THE COPOLYMER HAVING A MOLECULAR WEIGHT OF FROM 50,000 TO 2,000,000 AND A MINOR BUT LOAD CARRYING AND STABILIZING AMOUNT OF AN OILSOLUBLE DIVALENT METAL SALT OF A DIALKYL DITHIOCARBAMIC ACID, THE DIVALENT METAL BEING SELECTED FROM THE GROUP CONSISTING OF ZINC AND CADMIUM. 